UDP-glucose-glucan glucosyl-transferase activity of polymorphonuclear leukocytes from diabetic subjects.

Abstract

1. In normal leucocytes, glycogen-transferase was only found in the glucose-6-phosphate dependent D-form. An increase in activity was observed within 30 min after glucose feeding, and is assumed to be mediated through the action of released insulin. A late secondary increase in activity occurred simultaneously with an increase in serum growth hormone. — 2. In most diabetic leucocytes, glycogen-transferase was found in both the I- (independent of glucose-6-phosphate) and D-form. The I+D activity was low in uncontrolled diabetes and increased in response to insulin treatment. The I-activity was low immediately upon isolation of the leucocytes, but increased during incubation of the enzyme, especially in the presence of Mg2+; indicating that diabetic leucocytes possess transferase-D phosphatase activity in contrast to normal cells. The D to I transformation of the enzyme was greatly increased by insulin treatment. — 3. K m for UDPG and K a for glucose-6-phosphate did not vary between normal and diabetic leucocytes. — 4. The D to I interconversion of the incubated enzyme from diabetic cells was found to depend on the concentration of ATP and ADP in the incubation medium. It is suggested, that the activating effect of Mg2+ on the D to I transformation is due to an activation of an endogenous ATP-ase and adenylate kinase.